As many as 500 financial institutions will receive letters from HM Revenue & Customs by the end of March asking them to disclose details of UK taxpayers with accounts held offshore, Accountancy Age has learned.

According to a source familiar with the plans, contact with the banks would be the first stage in offering tens of thousands of account holders the opportunity to come clean, through a second offshore disclosure facility ­ or amnesty - on the funds they are holding overseas.

A spokesman for HMRC said as part of the first amnesty in 2007 the taxman wrote to customers of certain banks encouraging them to take advantage of the scheme’s fixed penalty opportunity, however many went unaccounted.

‘Clearly there are many people out there who will want to take advantage of a second scheme to put their minds at rest,’ he said.

The first amnesty tackled customers of the five major retail banks. Barclays, HSBC, HBOS, RBS and Lloyds TSB were urged to provide information relating to UK-based customers with offshore accounts.

An estimated 100,000 taxpayers were targeted by the first amnesty, of which 60,000 voluntarily disclosed information under the terms of the scheme. It netted HMRC approximately £400m, with the penalty applied capped at 10% of the outstanding tax owed plus interest.

The Special Commissioners gave HMRC authority to issue a notice to the banks concerned in the first amnesty and it is thought the same process will apply to the second round of disclosures.

HMRC refused to comment on specific financial institutions the department was intending to target.

According to Richard Murphy, tax campaigner at the Tax Justice Network, Swiss investment bank UBS could be a top target for HMRC after US authorities imposed a $780m (£537m) on the bank for failing to disclose the details of account holders.

Several tax experts told Accountancy Age they expect HMRC to target customers of Swiss and private banks, including SG Hambros and Credit Swiss.

Hambros declined to comment while the other banks were unable to respond before going to press.

Robert Kirkby, technical director at Jersey Finance, a government association for banks trading on the island, said HMRC could not be ‘too aggressive with a second amnesty’.